From: Frederic Weisbecker If RCU is waiting for the current CPU to complete a grace period, don't turn off the tick. Unlike dynctik-idle, we are not necessarily going to enter into rcu extended quiescent state, so we may need to keep the tick to note current CPU's quiescent states. [added build fix from Zen Lin] Signed-off-by: Frederic Weisbecker Cc: Alessio Igor Bogani Cc: Andrew Morton Cc: Avi Kivity Cc: Chris Metcalf Cc: Christoph Lameter Cc: Daniel Lezcano Cc: Geoff Levand Cc: Gilad Ben Yossef Cc: Hakan Akkan Cc: Ingo Molnar Cc: Kevin Hilman Cc: Max Krasnyansky Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Stephen Hemminger Cc: Steven Rostedt Cc: Sven-Thorsten Dietrich Cc: Thomas Gleixner Signed-off-by: Steven Rostedt --- include/linux/rcupdate.h | 1 + kernel/rcutree.c | 3 +-- kernel/time/tick-sched.c | 22 ++++++++++++++++++---- 3 files changed, 20 insertions(+), 6 deletions(-) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 7c968e4..9804c3a 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -186,6 +186,7 @@ static inline int rcu_preempt_depth(void) extern void rcu_sched_qs(int cpu); extern void rcu_bh_qs(int cpu); extern void rcu_check_callbacks(int cpu, int user); +extern int rcu_pending(int cpu); struct notifier_block; extern void rcu_idle_enter(void); extern void rcu_idle_exit(void); diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 74df86b..0dca81f 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -234,7 +234,6 @@ module_param(jiffies_till_next_fqs, ulong, 0644); static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)); static void force_quiescent_state(struct rcu_state *rsp); -static int rcu_pending(int cpu); /* * Return the number of RCU-sched batches processed thus far for debug & stats. @@ -2429,7 +2428,7 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) * by the current CPU, returning 1 if so. This function is part of the * RCU implementation; it is -not- an exported member of the RCU API. */ -static int rcu_pending(int cpu) +int rcu_pending(int cpu) { struct rcu_state *rsp; diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 35047b2..de3c8fe 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -512,9 +512,21 @@ void tick_nohz_idle_enter(void) local_irq_enable(); } +#ifdef CONFIG_CPUSETS_NO_HZ +static bool can_stop_adaptive_tick(void) +{ + if (!sched_can_stop_tick()) + return false; + + /* Is there a grace period to complete ? */ + if (rcu_pending(smp_processor_id())) + return false; + + return true; +} + static void tick_nohz_cpuset_stop_tick(struct tick_sched *ts) { -#ifdef CONFIG_CPUSETS_NO_HZ int cpu = smp_processor_id(); if (!cpuset_adaptive_nohz() || is_idle_task(current)) @@ -523,12 +535,14 @@ static void tick_nohz_cpuset_stop_tick(struct tick_sched *ts) if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE) return; - if (!sched_can_stop_tick()) + if (!can_stop_adaptive_tick()) return; tick_nohz_stop_sched_tick(ts, ktime_get(), cpu); -#endif } +#else +static void tick_nohz_cpuset_stop_tick(struct tick_sched *ts) { } +#endif /** * tick_nohz_irq_exit - update next tick event from interrupt exit @@ -860,7 +874,7 @@ void tick_nohz_check_adaptive(void) if (cpuset_adaptive_nohz()) { if (ts->tick_stopped && !is_idle_task(current)) { - if (!sched_can_stop_tick()) + if (!can_stop_adaptive_tick()) tick_nohz_restart_sched_tick(); } } -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/